I think that Harold is right on the mark. We can get to a point where
information that is initially shared with the public (irrespective of
medium - although sharing online has to be the most saturated type of
sharing there is that is open to the largest number of participants),
is meant for use by the public. To create additional obstacles to its
use beyond the recognition of the initial source, seems to be to put
the kibosh on the whole point of using the medium and sharing the
information to begin with. Not to trivialize the matter, but once the
horse has been let out of the barn, it does seem a bit futile to take
pains to close the door after the fact...